The present invention relates to the lighting arts. It especially relates to high intensity light emitting diode chip packages, components, apparatuses, and so forth, and will be described with particular reference thereto. However, the invention will also find application in conjunction with other solid state light emitting chips such as vertical cavity surface emitting lasers, organic light emitting chips, and the like.
High power light emitting diode packages employ one or more light emitting chips operating at relatively high current levels to produce high brightness or high light output intensities. A light emitting diode chip has a voltage drop which typically is determined largely by the band gap of the material. The operating voltage of a light emitting diode chip is typically about 4 volts or less. Thus, generating high light output intensities involves increasing the operating current to increase the input power level. A high operating current, in turn, leads to high resistive losses in cladding layers, electrodes, wire bonds, printed circuit traces, or other electrically resistive elements in the current path.
These resistive losses translate into substantial heating of the light emitting package when operated at high power levels. Heating can produce thermal degradation of the light emitting diode chip, the chip electrodes, sealing encapsulant, solder bumps, or other components of the light emitting package. Moreover, heating generally increases the resistance of the electrical pathways and can reduce the light emission efficiency. As a consequence, the light output power increase is proportionally smaller than the input electrical power increase.
Various thermal management techniques have been employed in light emitting diode packages. Encapsulating epoxies, sub-mounts, and the like are selected to provide high thermal conductivity to promote heat transfer away from the operating light emitting diode chips. Heat sinks are provided to collect and dissipate the generated heat. Chip electrodes are distributed across the chip area to provide current and heat distribution. Encapsulants and other thermally sensitive materials are chosen for good thermal stability and robustness. These design techniques reduce, but do not eliminate, thermal concerns in high brightness light emitting chip packages.
The present invention contemplates improved apparatuses and methods that overcome the above-mentioned limitations and others.